Tens of thousands of dead fish emerged in the Peconic Estuary on Friday, prompting officials to organize cleanup efforts Saturday.

The dead bunker fish -- a bait fish for predators such as bluefish -- were spotted floating in the Peconic River, Meeting House Creek, Sawmill Creek and Indian Island Golf Course in Riverhead, as well as in Reeves Bay in Flanders and down the adjoining coast bay side, according to Riverhead Town Supervisor Sean Walter and Southampton Town Supervisor Anna Throne-Holst.

"This morning there was almost wall-to-wall fish down here and further west by Colonel's Island," said Walter, standing along the Peconic Riverwalk on Saturday afternoon.

Thousands of dead bunker fish cover the shore at Indian Island County Park Beach in Riverhead on Sunday, May 30, 2015. Photo Credit: Randee Daddona

Walter considered declaring a public health state of emergency until winds pushed the fish to the Peconic Bay.

"Hopefully, they will just sink into the bay bottom rather than come up here and sink in the river," he said.

State Department of Environmental Conservation officials surveyed the area Friday and found that depths beyond 3 feet did not have enough oxygen for the fish, Walter said.

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Piles of fish were seen at Indian Island County Park Beach in Riverhead. Calls and emails to a Suffolk County spokesman were not immediately returned.

Ed Warner Jr., president of Southampton Town Trustees, said the estuary has been beset by fish kills in recent years.

"Every year, we have more and more bunkers that come into Peconic Bay to spawn," he said. Predator fish push large schools of bunkers into the Peconic River, "which is a very confined area of shallow water, and they basically run out of oxygen and suffocate," he said.

Southampton Town marine maintenance crews hauled dead fish from sandy beaches in Southampton and Flanders on Friday and Saturday morning, said Warner, adding, "A lot of people live around the water . . . the smell from the fish decomposing is not a pleasant smell."

Christopher Gobler, professor of marine science at Stony Brook University who researches Long Island's coastal waters, said the massive fish kill was caused by low oxygen stemming from "a very dense algae bloom in the region" formed by high levels of nitrogen.

Nitrogen can be generated by runoff from neighboring development, an adjacent sewage treatment plant and residential cesspools, Gobler said. "There are lots of sources . . . so there needs to be efforts to reduce the nitrogen-loading," he said.

Southampton Town officials are monitoring the winds and tides, which determine where larger masses of bunker fish will appear, Throne-Holst said.

Riverhead Town officials are also monitoring the winds and keeping a crew of about six fishermen on standby if needed to net fish in the coming days. The fish would be buried at either the Brookhaven Town or Riverhead Town landfill.

Riverhead Town residents who need help cleaning up fish on their property can call the supervisor's office at 631-727-3200, ext. 655.